What Is The Best Material For Energy Efficient Exterior Doors?

What is the best material for energy efficient exterior doors?

When it comes to home energy efficiency, one area that is often overlooked is exterior doors. Selecting exterior doors made from materials with high insulating properties can make a big difference in preventing heat loss and reducing energy costs. The goal of this article is to identify the best material choice for energy efficient exterior doors by comparing factors such as R-value, durability, climate suitability, and cost.

Energy Efficiency Ratings

When shopping for an energy efficient exterior door, there are three key ratings to look for:

R-value – This measures the door’s resistance to heat flow. The higher the R-value, the better the insulating properties. Look for a door with an R-value of 2 or higher (Energy.gov).

U-factor – This gauges how well the door prevents heat from escaping. The lower the U-factor, the better. Aim for a U-factor of 0.25 or less (HouseLogic).

Air Infiltration – Measures how much outside air leaks through the door. Look for a rating of 0.30 cfm/ft2 or less (Energy.gov).

Common Door Materials

There are several common materials used for exterior doors. The most popular options include:


Wood doors are a classic choice that provide a traditional, natural look. Some benefits of wood include:

  • Aesthetically pleasing and available in many styles
  • Good insulation properties to maintain indoor temperatures
  • Durable when properly maintained

However, wood doors require more maintenance such as regular refinishing to prevent moisture damage. See: https://nextdoorandwindow.com/best-material-for-entry-door/


Steel doors are known for their strength, security, and durability. Pros of steel include:

  • Very strong and secure against forced entry
  • Low maintenance
  • Affordable option

The main downside is that steel can dent and lacks insulation without added panels or cores. See: https://www.zeelandlumber.com/fiberglass-vs-wood-vs-steel-which-type-of-exterior-door-is-right-for-you/


Fiberglass doors are growing in popularity due to their durability and low maintenance. Benefits include:

  • Impact resistant and won’t warp or crack
  • Good insulation properties
  • Various styles and finishes available

Fiberglass doors can be more expensive than other options. The surface may also require refinishing over time.


Composite doors combine materials like wood, fiberglass, steel, and foam insulation for enhanced performance:

  • Very durable and low maintenance
  • Good security features
  • Excellent insulation and energy efficiency

Composites are typically the most expensive type of exterior door.


Wood is a natural insulator and has been used for centuries to make exterior doors (source). Solid wood doors with tight grain patterns provide decent thermal resistance and can block drafts when properly weather-stripped and sealed. Although basic wooden doors lose some efficiency due to knots and cracks that develop over time, advanced wood doors made of engineered lumber or solid wood cores can match or exceed the insulation of metal and fiberglass doors (source).

The natural insulating properties of wood mean that solid wood doors can be manufactured to be highly energy efficient. Multiple layers of wood with staggered seams create thermal breaks that reduce conduction. Improved door frames and advanced weatherstripping further reduce air infiltration. With the right construction, wood doors can achieve U-factors around 0.17, comparable to the best fiberglass models (source).

However, wood doors are prone to moisture damage and swelling if the exterior is not properly sealed. Regular maintenance is required to refinish and seal the wood from weathering. Improperly sealed doors can warp or crack over time, reducing energy efficiency. Frequent inspection and upkeep is necessary for wood doors in harsh climates (source).


Steel is a popular choice for exterior doors due to its durability and security. When it comes to energy efficiency, steel has some advantages and disadvantages.

On the plus side, steel is a good conductor of heat and can achieve high R-values with proper insulation. Steel doors with a foam core insulation and weatherstripping can rate very well on energy efficiency tests. According to the Steel Door Institute, “The reason energy efficient steel doors work so well is because of their unique construction. Hollow metal doors are two pieces of steel with insulation material sandwiched between them” (https://steeldoor.org/energy-efficient-doors/).

However, steel doors can be prone to condensation since the metal conducts heat and cold easily. Insulation and weatherstripping are important to prevent temperature transfer and moisture buildup.


Fiberglass is gaining popularity as a material for energy efficient exterior doors. Fiberglass doors provide excellent insulating properties compared to wood or steel. The material is lightweight yet very strong and durable. It resists damage from weather, rotting, warping, shrinking, and swelling. Fiberglass won’t rust or dent like metal doors. The smooth non-porous surface also resists scratching and staining.

Fiberglass doors can be stained or painted to match the look of wood styles. The material can be molded into various designs to replicate stained wood doors or painted doors with intricate detailing. Fiberglass is a great option for exterior doors in high-traffic areas or extreme climates. It provides thermal efficiency for energy savings while looking like a traditional wood door.


Composite doors are made from a combination of materials to maximize energy efficiency, durability, and aesthetics. They typically consist of a thermally insulating foam core sandwiched between two fiberglass or steel skins. This allows composite doors to balance the pros and cons of different materials (source).

The insulating foam core prevents heat transfer and helps block outside noise. Fiberglass skins provide strength while remaining lightweight. The composite construction makes doors highly tuneable – manufacturers can adjust the thickness and density of foam, as well as the types of skins used, to achieve the desired thermal efficiency, security, and visual look (source).

Other Considerations

Besides just the door material, there are some other factors that affect a door’s energy efficiency:


Doors with glass panes, also known as glazing, tend to be less energy efficient. Glass has a lower R-value than most door materials so it allows more heat transfer. Having multiple panes with argon gas in between can improve the insulation of glass. Also, look for glazing with low-e coatings to reduce solar heat gain (source: https://gbdmagazine.com/energy-efficient-doors/).

Weather Stripping

Ensure the door has quality weather stripping around the edges to seal air leaks. The weather stripping material matters – foam strips may degrade faster than rubber or vinyl options. Replace worn out weather stripping to maintain energy efficiency (source: https://blog.constellation.com/2020/11/30/energy-efficient-doors/).


Proper installation is crucial. Gaps around the edges of the door frame can let in drafts. Make sure the door is plum, level, and seals tightly all the way around the frame when closed. Use shims during installation if needed. Caulk around the exterior frame to seal any remaining air leaks (source: https://www.masonite.com/discover-and-learn/front-door-impacts-energy-efficiency/).


Based on the benefits and drawbacks of each material, fiberglass is generally the top recommendation for the most energy efficient exterior door. Fiberglass doors have high insulation values, typically around R-5 to R-6, which significantly reduces heat transfer and improves energy efficiency. The composite material prevents air infiltration better than wood. Fiberglass is also highly durable, dent-resistant, and low maintenance compared to wood or steel.

While wood doors can be energy efficient with multiple panes of glass and weatherstripping, they are prone to expanding and contracting and letting in drafts. Steel doors are very durable, but not as insulating. Some composite doors offer similar efficiency to fiberglass, but fiberglass edges out as the top choice for its superior insulation, weatherproofing abilities, and durability.

In summary, fiberglass exterior doors are recommended as the best option for energy efficiency based on their excellent thermal performance, tight weather seals, durability, and low maintenance requirements. The insulation properties allow fiberglass doors to reduce energy costs and improve home energy efficiency more than other common door materials.


When it comes to selecting the most energy efficient exterior door material, there are a few key factors to consider. As outlined above, wood, steel, fiberglass, and composite materials each have their own advantages and disadvantages regarding insulation value, durability, longevity, and cost.

Wood doors can provide good insulation, but they may be prone to swelling and warping. Steel is very durable, but not as insulating. Fiberglass has good insulation properties, but lacks the aesthetics and feel of real wood. Composites like fiberglass with a wood veneer offer a compromise.

Overall, fiberglass and composite doors rate well for energy efficiency. They have insulation values comparable to wood, but avoid issues with moisture and warping. Durability is also better than wood. For cold climates, choosing an insulated steel door with a fiberglass or composite skin can optimize energy efficiency.

When selecting an exterior door, carefully compare insulation ratings, materials, styles and costs. For optimal energy efficiency, durability, and aesthetics, a fiberglass or composite door is likely the best option. Proper installation and weatherstripping are also key. With energy efficient doors, you can help reduce heating and cooling costs while beautifying your home.

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